Magnetically controlled electron tube function generator

ABSTRACT

A function generator. An electron tube is provided having a cathode, and an anode coextensive with and spaced from the cathode so as to form a gap therebetween. The anode is at a higher potential than the cathode so as to create an electric field between the anode and the cathode. A means for obtaining an output from the function generator as a desired function of the input to the function generator is also provided. This means includes a means for providing a magnetic field in the gap which is normal to the electric field and further includes means for varying the direction of the magnetic field. The variation in the electric field is obtained by varying the width of the gap in the direction of the longitudinal axis of the tube. The variation in the magnetic field is obtained by varying the intensity of the magnetic field in the direction of the longitudinal axis of the tube. By use of additional magnetic fields or by separating the cathode and anode into distinct portions, or a combination thereof multiple functions may be provided.

United States Patent Snow 1451 May 2,1972

William W. Snow, 3250 54th Street, Woodside, NY. 11377 [22] Filed: Apr. 7, 1970 [21] Appl. No.: 26,190

[72] Inventor:

[52] U.S.Cl ..328/253,328/249,313/153,

313/154, 313/156, 315/3967 [51] Int. Cl. ..1-10lj2l/18 [58] Field ofSearch ..313/l53.154,155,156,157.

[56] References Cited UNITED STATES PATENTS 3,506,870 4/1970 Singer et al ..313/153 Primary Examiner-John W. Huckert Assistant ExaminerAndrew .1. James Attorney-Hubbell, Cohen & Stiefel ABSTRACT A function generator. An electron tube is provided having a cathode, and an anode coextensive with and spaced from the cathode so as to form a gap therebetween. The anode is at a higher potential than the cathode so as to create an electric field between the anode and the cathode. A means for obtaining an output from the function generator as a desired function of the input to the function generator is also provided. This means includes a means for providing a magnetic field in the gap which is normal to the electric field and further includes means for varying the direction of the magnetic field. The variation in the electric field is obtained by varying the width of the gap in the direction of the longitudinal axis of the tube. The variation in the magnetic field is obtained by varying the intensity of the magnetic field in the direction of the longitudinal axis of the tube. By use of additional magnetic fields or by separating the cathode and anode into distinct portions, or a combination thereof multiple functions may be provided.

21 Claims, 32 Drawing Figures 2,227,909 1/1941 Ohl ..313/156 X 2,246,121 6/1941 Blewett ..313/156 X 2.941.099 6/1960 Picard et a1 ..313/153 X R25,420 7/1963 Vaughan et a1.. .1..313/153 X 3,387,165 6/1968 Boucher ..313/156 48 gHHH 3 161141, 48

PATENTEDMAY 2 I972 SHEET 1 OF 3 w m w &- Q m H M & M 3 M T G I 8 4 M NOW ATTORNEYS INVE OR WILLIA jPLATE CURRENT (m a) PLATE CURRENT PATENTEIIIIIII 2 I972 3, 660, 770

SHEET 2 BF 3 SIMPLE DIODE CHARACTER- ISTIC I/,CHARACTERISTIC rWITH AXIAL I MAGNETIC FIELD IN DIRECTION OF I, CHARAECTERISJBC e PLATE VOLTAGE 3 FIG. IO.

VOLTAGE CURRENT CHARACTERISTIC WITH AT LEASTONE FIELD IN GAP VARYING I VOLTAGE CURRENT I CHARACTERISTIC rwITII UNIFORM AXIAL MAGNET! I FIELDS IN GA FIELD INVENTOR WILLIAM SNOW MINI, 09 mg ATTORNEYS.

PATENTEIIIIIY 2 IIIII SHEET 3 0F 3 FIG. 3!.

-- INPUT OUT PUT (HALF-wAvEI OUTPUT (FULL WAVE) 1 I I I I I II II Mai/I6 in; 6 48 I v I20 [2 2 50 INVENTOR v 45 BY WILLIAM SNOW IMIIMI ATTORNEYS MAGNETICALLY CONTROLLED ELECTRON TUBE FUNCTION GENERATOR BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to function generators, and more particularly to magnetically controlled electron tube function generators.

2. Description of the Prior Art It is a well known principle of electron physics that an electron moving through a magnetic field which is perpendicular to the direction of movement of the electron will experience a sideways magnetic force which will act on the moving charge.

This phenomenon is represented by the mathematical expression F=qv X B, wherein F represents the magnitude of the deflecting force, v represents the velocity of the moving electron, q represents the charge on the moving electron and B represents the basic magnetic field vector characteristic of the magnetic field strength and is commonly termed magnetic induction. The deflecting force F on the moving charge is perpendicular to the path of movement of the electron, and the electron circulates at right angles to the magnetic field. When the magnetic and electric fields are normal to each other this tends to bend the electron path into a circle. The radius of the circular path may be defined by the expression r=mv/qB, wherein m represents the mass of the electron particle, v represents the velocity of the electron particle, q represents the charge on the electron particle and B represents the magnetic induction associated with the magnetic field. This is the principle utilized in the cyclotron and other magnetically controlled devices.

lt is another well known principle of electron physics that electrons traveling through a wire, which is commonly termed a current, produce a magnetic field about the wire (Oersteds principle). Amperes Law expresses the quantitative relationship between the current I and the magnetic flux density B as B =(2 J/r), where B is the flux density at a point a perpendicular distance r from the wire, I is the current in the wire, and p. is a constant representing the magnetic permeability of the medium (u is equal to l in a vacuum). Applying Amperes Law to a current carrying wire arranged in a coil or helix, the magnetic flux density B may be represented by the expression B n-i -N, where i represents the current flowing through the coil, and N the number ofturns ofwire per unit length.

As can be seen, this expression is solely dependent on the current i, and number of turns of wire per unit length N, the flux density B varying as either N or i varies. This principle is utilized to provide magnetic fields from inductors.

Another well known principle of electron physics, is that the strength of the electrostatic, hereinafter referred to as electric, field between two charged plates is inversely dependent on the square of the distance between the plates. As the spacing between the plates varies the strength of the electric field varies inversely. This principle has been utilized to provide uniform electric fields in the region between the electrodes of electron tubes.

One such magnetically controlled device which utilizes these principles of electron physics is commonly termed a magnetron. The magnetron is a diode tube whose current is influenced by a magnetic field. The diode tube has a cathode and an anode spaced therefrom to form a gap therebetween. The anode or plate is normally kept at some positive potential with respect to the cathode so as to create an electric field therebetween. The cathode extends along the longitudinal axis of the tube and the anode is annular and coaxial with the cathode and uniformly spaced therefrom to provide a uniform electric field. A magnetic field which is normal to the electric field is applied to the gap formed therebetween the cathode and the anode of the tube and has a uniform field strength longitudinally in the direction of the longitudinal axis of the tube. In the absence of a magnetic field the electrons travel to the plate in a straight path. However, as the magnetic field is applied and increased in intensity, the electron path becomes curved in circular paths of decreasing radius.

Magnetrons make use of the aforementioned principles of electron physics so as to vary the radius of the circular path and control conduction in the tube. In this manner, at a certain critical value of the field intensity B, the electrons will miss the anode entirely and return to the cathode in a circular orbit. At this point no anode current flows and the tube does not conduct. This point is termed plate-current cutoff. At higher values of field intensity B, the radii of the circular orbits become smaller. At lower values of the field intensity B, the radii of the circular orbits become increasingly larger and the electron paths are intercepted by the anode. The intercepted electrons strike the anode and cause conduction resulting in a plate current. In this manner a magnetic field is utilized to control the flow of electrons in a diode tube, which effectively functions similar to a conventional triode with the magnetic field replacing the electrostatic control grid. Conventional magnetrons, in which the design parameters are known, utilize a permanent magnet rather than an induction coil to provide the desired magnetic field strength.

In conventional magnetrons, values of magnetic and electric field strength are selected which permit the electrons to travel in a spiral path about the longitudinal axis of the tube and form a rotating swarm of gyrating electrons. The purpose of this is to generate high frequency oscillations. These high frequency oscillations, as will be explained in greater detail hereinafter, are due to energy transfer from the swarm of gyrating electrons to a resonant cavity within the tube structure. The frequency of oscillation is determined by the resonant cavity frequency. Another condition which is necessary to sustain the magnetron oscillations is that the transit time of the electrons, which is the time for the electrons to complete their passage from cathode to anode, is of the same order of magnitude as one period of oscillation. It is important to the operation of conventional magnetrons that the magnetic and electric fields applied to the gap be uniform throughout along the longitudinal axis of the tube. These limiting features of conventional magnetrons has resulted in their use only for super-high-frequency oscillators and amplifiers.

These super-high-frequency oscillators are primarily of the multicavity resonator type. This type of tube has a cathode cylinder of appreciable diameter located in a cavity in the center of the structure. The plate or anode is formed by cutting a cylindrical hole in a metal block into which the cathode is positioned so as to form an annular gap of proper thickness. The cavities are cut out of the block in the fonn of cylindrical holes and slots, or other shapes which divide the anode into a plurality of segments and form the resonators which establish the oscillations and determine their frequency. In the hole-and-slot type of resonator, each slot and terminating hole is electrically equivalent to a tuned resonant circuit, the slot having predominantly capacitive action, and the terminating hole being primarily inductive. Under proper conditions of voltage and magnetic field strength, energy is transferred from the swarm of gyrating electrons to the resonant cavities and powerful oscillations are sustained. Although the magnetron oscillator and amplifier have been of considerable importance, its construction has limited its application to only these functions.

SUMMARY A magnetically controlled electron tube function generator is provided with a cathode and an anode coextensive with and spaced from the cathode so as to form a gap therebetween. The anode is at a higher potential from the cathode so as to create an electric field therebetween. A means for obtaining a voltage or current output from the function generator as a desired function of a voltage or current input to the function generator is also provided. This function obtaining means includes a means for providing a magnetic field to the gap which is normal to the electric field and further includes means for varying at least one of the fields present in the gap along the direction of the magnetic field. The function is due in essence to this variation. The strength of the electric field in the gap is varied by shaping the gap to be of non-uniform width along at least a portion of the length of the cathode. In order to vary the width of the gap, the face of the anode opposite the cathode is shaped, although the cathode may be shaped instead. The strength of the magnetic field in the gap may also be varied by varying the magnetic field intensity along the length of the cathode which partially defines a gap of uniform width. Both the magnetic and electric fields present in the gap afiect the function produced by the function generator and a combination of the two aforementioned means for varying the strength of these fields may also be employed. The magnetic field is due to a magnetic field providing means which is arranged to apply a magnetic field which is normal to the direction of the electric field. This means is arranged in surrounding relation with the anode. By varying the strengthof a field within the gap to a desired amount, a large variety of functions may be generated by this function generator.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partly diagrammatic and partly sectional view of the preferred embodiment of the present invention;

1 FIG. 2 is a sectional view taken along line 2-2 of FIG. 1;

FIGS. 3, 5 through 8, 22 and 25 are views similar to FIG. 1, illustrating alternative embodiments of the present invention;

FIG. 4 is a sectional view taken along line 44 of the embodiment shown in FIG. 3; I

FIGS. 9 and 10 are graphical illustrations of the principles associated with the present invention.

FIGS. 11 through 21, 23 and 24 are schematic diagrams of various possible circuit configurations for the embodiment of the present invention;

FIGS. 26 through 30 are graphical illustrations of typical functions associated with the embodiment of the present invention; and

FIG. 31 is a graphical illustration of a functionassociated with a particular circuit configuration of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings in detail and particularly to FIGS. 1 and 2, a controlled electron tube function generator, generally referred to by the reference numeral 40 includes a cathode 42, an anode 44 coextensive with and spaced therefrom so as to form gap 46 between the anode 44 and cathode 42, and a means for obtaining an output from the function generator 40 as a desired function of the function generator input. As in conventional electron tubes, the anode is at a different potential from the cathode so as to create an electric field therebetween. A means 48 is provided for applying a magnetic field to the gap 46 which magnetic field is essentially normal to the electric field. This field providing means is preferably an air core coil 48 having a current applied thereto although an iron core coil, permanent magnet, or combination may be utilized depending on the desired field configuration for the field providing means. In accordance with the present invention at least one of the fields present in the gap 46 is varied in the direction of the magnetic field. In this manner, a variety of functions of the tube input which are preferably of the monotonic type, (a function whose first derivative does not change sign), may be obtained for the output of the function generator.

As may be seen in FIG. 1, the anode 44, which has an inner wall 66 and an outer 50 wall, and the cathode 42 are shown to extend in the direction of the longitudinal axis of the tube 40,

. with the anode 44 preferably in surrounding relation with the cathode 42. Preferably the cathode 42 is disposed along the tube axis and the anode 44 is preferably cylindrical and coaxial therewith. As shown the cathode 42 is indirectly heated to cause electron emission but may be heated in any conventional manner, such as directly, to accomplish this purpose. The coil 48 provides a magnetic field to the gap 46 of uniform intensity, and the coil is preferably disposed in surrounding relation with the outer wall 50 of the cylindrical anode 44 so as to provide an axial magnetic field. Current is applied to the coil 48 so as to produce the magnetic field. By applying the simple right hand rule of electron physics, the direction of the magnetic field, or flux lines, can be determined. The direction of the magnetic field is illustrated by the flux lines 51 in FIG. 1.

The input to the coil 48, which is represented by the voltage V,,, and current I,,,, is applied to the coil 48 soas to produce the magnetic field represented by the flux lines 51. This field provides the magnetic control for the tube 40. A voltage V,, is applied to the anode 44, so as to provide a potential difference between the anode 44 and the cathode 42 and thus create an electric field in the gap 46 which acts to attract electrons present in the gap 46, such as those emitted from the cathode by cathode emission, to the anode 44. The electric field present in the gap 46 is essentially normal to the axial magnetic field.

As is shown in FIG. 2, in the absence of the axial magnetic field, cathode emitted electrons which enter the gap 46.wil] follow a straight line path 49, to the anode 44. 7

As current I,, begins to flow in the coil 48, and the axial magnetic field is produced, the electrons follow a curved circular path 54, of large radius r which is greater than the gap radius r,,. Thus, the electrons continue to move across the gap to anode 44. As the current I increases the magnetic field intensity increases and the radius of the circular path r. is thus reduced until it is slightly less than the gap radius r, at which point no electrons reach the anode 44 and the tube is cut-off.

FIG. 9 represents a comparison of the plate current-plate voltage characteristics 56 and 58 respectively, of a simple diode and a diode tube having an axial magnetic field applied thereto, both electric field and axial magnetic field being uniform along the axis of the tube. As can be seen, the characteristic 58 for the diode tube with the axial magnetic field is similar to the characteristic 59 of a conventional triode, having a grid voltage, e.g., which is some negative valve -V, wherein conduction does not occur until the plate voltage overcomes the cut-off action of the control means (control grid fora triode, or magnetic field for the magnetically controlled tube).

FIG. 10 represents a comparison of the voltage-current characteristics for a magnetically controlled electron tube 60 having uniform electric and magnetic fields along the axis of the tube, and one 62 having either electric or magnetic fields, or both, which vary along the axis of the tube, as in the present invention. As can be seen by comparing the two curves 60 and 62, the characteristic 60 for the tube with uniform fields is much steeper, with current beginning to flow at a much higher voltage, than the characteristic 62, which has non-uniform electric and magnetic fields. The absence of a sharp cut-off in a tube in which the electric or magnetic fields vary along the length of the tube is due to the fact that cut-off results from the deflecting force F on the electrons being sufficient along the entire length of the tube to prevent their reaching the anode along its entire length. When the field, either electric or magnetic, is varied along the tube length, the deflecting force sufficient to prevent electron flow will not be achieved at the same instant in every transverse plane. If, for example, the magnetic field strength is uniform, but the electric field is varied as shown in FIG. 1 and explained in greater detail hereinafter, the deflecting force F will be large enough to prevent current flow in the transverse plane of minimum electric field before it is large enough to prevent current flow along the transverse plane of maximum electric field and the same is true for the electric field where the electric field is uniform and the magnetic field is varied, as shown in FIG. 8 and explained in greater detail hereinafter. Thus, the curve of field distribution along the length of the gap 46 can shape the curve 62. As will be better understood hereinafter, means are available for variously shaping the field distribution curve whereby to give rise to a variety of I, vs. V, curves. A variety of functions may be obtained from a tube having gradual cut-off characteristics such as illustrated by curve 62.

In order to provide a varying electric field to the gap 46, in the preferred embodiment shown in FIG. 1, the cylindrical anode inner wall 66 has a portion 68 which is non-uniformly spaced from the cathode 42 along at least a portion of the length of the cathode 42. The size of the gap is thereby varied in the direction of the longitudinal tube axis. With a magnetic field of uniform intensity and a varying gap, the electric field within the gap varies in accordance with the variations in the size of the gap. Therefore, in this manner, the electric field within the gap 46 is varied in the direction of the longitudinal tube axis. The anode inner wall 66, as shown and preferred, has another portion 70 which is uniformly spaced from the cathode 42. The portion 70 that is uniformly spaced from the cathode 42 determines the minimum anode potential necessary for conduction. The length of this portion 70 may be any desired length, the length depending on the desired function. This portion 70 determines the minimum anode potential necessary for conduction due to the fact that the nonuniformly spaced portion 68 of the inner wall 66 is inwardly tapered toward the cathode 42 to the point at which the uniformly spaced portion 70 begins. The uniformly spaced portion 70 is therefore at the minimum spacing from the cathode 42, so as to provide the minimum size gap 46. Therefore, in order to start conduction within the tube 40 an anode potential which is merely sufficient to overcome the effect of the magnetic field within this minimally spaced uniform gap need be applied to the anode 44. As the anode potential is increased, the effects of the magnetic field are sequentially overcome as the non-uniform spacing increases, until there is sufficient anode potential applied to overcome the effects of the magnetic field at the point of maximum spacing from the cathode 42. In this manner, conduction will occur throughout the entire anode 44. As was previously mentioned, it is the shape of the anode 44, and hence the gap 46 which determines the cut-off characteristic of the tube which is gradual due to the tapering of the gap 46. Referring now to FIG. 5, the tube 71 is similar to that shown in FIG. 1, but with the relative shaping of the cathode 72 and anode 74 reversed from that shown in FIG. I. The anode 76 is cylindrical and has a uniform radius in the direction of the longitudinal tube axis and the cathode 72 is, shaped to provide a non-uniform gap 74, and thus vary the electric field contained therein in the direction of the longitudinal tube axis. The anode 76 has an inner wall 82 and an outer wall 83, and the cathode 72 has an outer wall 78. The cathode outer wall 78 has a portion 80, which is outwardly tapered toward the anode inner wall 82 along at least a portion of the length of the anode 76, to render portion 80 nonuniformly spaced from the cathode along their longitudinal axis. As preferred, the cathode outer wall 78 has another portion 84 which is uniformly spaced from the anode inner wall 82. The non-uniformly spaced portion 80 is outwardly tapered until the point at which the uniformly spaced portion 84 begins. The uniformly spaced portion 84 is therefore at the minimum spacing from the anode 76 so as to provide the minimum size gap in the embodiment of FIG. 1.

in the embodiment shown in FIG. 6, both anode 86 and cathode 88 have non-uniform portions that jointly define the non-uniform gap portion along at least a portion of the respective lengths of anode and cathode. The anode 86 has an outer wall 91 and an inner wall 90, and the cathode 88 has an outer wall 94. The anode inner wall 90 has a non-uniform portion 92 which is inwardly tapered toward the cathode outer wall 94 along at least a portion of the length of the cathode 88. The cathode outer wall 94 has a non-uniform portion 96 which is outwardly tapered toward the anode inner wall 90 along at least a portion of the length of the anode 86, and preferably along the same length as the inwardly tapered portion 92 of the anode 86. Both the anode 86 and cathode 88 preferably have a uniform cylindrical portion 98 and 100, respectively, which are opposite each other and are located at the end of the respective tapered wall portions 92 and 96 to define the minimum size gap between the anode 86 and cathode 88. This minimum size gap functions in the same manner as the minimum size gap of the embodiment shown in FIG. 1.

Referring now to FIG. 8, an alternative means is shown for varying the field present in the gap along the longitudinal axis of the tube. In this embodiment, the magnetic field in the gap is varied rather than the electric field. The electron tube 140 includes a uniformly cylindrical cathode 142 preferably disposed along the longitudinal axis 143 of the tube, and a uniformly cylindrical anode 144, preferably concentric and in surrounding relation with the cathode 142 to define a uniform gap 146. The anode 144 and the cathode 142 are electrically connected together through a power source V,, as in the embodiment shown in FIG. 1, so as to provide a positive potential to the anode 144 with respect to the cathode 142 and thus create an electric field therebetween. This electric field is uniform along the longitudinal axis of the tube due to the uniform gap. A coil 148 is disposed adjacent to the anode outer wall 150 in surrounding relation with the anode 144 and preferably is concentric with the anode 144 and longitudinally extends along the entire length of the anode 144. As can be seen in FIG. 8, coil 148 is not distributed uniformly along the length of anode 144, as were the coils of the FIGS. 1 and 5 embodiments, to yield a uniform flux density along the length of the anode. Instead, coil 148 is non-uniformly distributed. As shown for illustrative purposes in FIG. 8, there are many more turns per unit length of anode near the bottom thereof than near the top, whereby to cause a greater flux density near the bottom than near the top. As the gap width is constant, the electric field is uniform and the magnetic field present in the gap varies in accordance with the longitudinal variation in flux density. The functions which may be derived from a tube 140 constructed in this manner are similar to the functions which may be derived from the embodiment shown in FIG. 1. As will occur to one skilled in the art, either the number of turns N of conductor wire comprising the coil 148 can be varied, the coil itself can be longitudinally moved in the direction of the longitudinal axis 143 of the tube 140, or the diameter of the coil 148 can be varied along its length so as to easily change the function associated with the tube 140. Various other methods of varying the magnetic field present in the gap will occur to one skilled in the art. For example, if desired, the coil 148 may be replaced by a cylindrical permanent magnet (not shown) which is tapered along its length in the direction of the longitudinal axis of the tube so as to vary the magnetic field intensity B associated therewith. By utilizing the principles associated with the above described embodiments, a magnetically controlled electron tube capable of providing a wide range of function generation within very broad voltage limitations can be obtained. The relationship between the input voltage and output current in the tubeoutput can be any desired monotonic function.

Referring now to FIGS. 26 through 30 inclusive, a variety of functions which can be generated by the constructions of the present invention are shown for purposes of illustration. In the graphic illustration of FIGS. 26 through 30 inclusive, the input voltage V,, is plotted against the output current I V and V, represent the extents of the control range voltage and V represents the nominal operating voltage. FIG. 26 represents a positive monotonic function for the output wherein I,, increases along a curve of varying slope with an increase in input voltage V, within the control range from V to V,;,. The operation of the tube outside the control range V to V (as shown in FIGS. 26 through inclusive) is represented by positively increasing lines, which represent the combination of the voltage-current characteristics of the inductor and tube comprising the function generator in the circuit arrangement required for these functions.

Referring now to FIG. 27, a positive linear function is shown wherein the output current 1,, increases along a straight line path within the control range V to V,;;, as the input voltage V, increases.

Referring now to FIG. 28, a constant current function is shown, wherein the output current I remains constant throughout the control range V to V as the input voltage V, to the tube increases. This particular function has wide application as a constant current source, as will be explained in greater detail hereinafter.

FIG. 29 represents anegative linear function for the output current I,,, wherein as the input voltage V, increases within the control range V to V the output current I decreases along a straight line path.

Referring now to FIG. 30, a negative monotonic function of the output current 1,, is shown wherein the output current I decreases along a curved path within the control range V to V as the input voltage V, increases.

The slopes of the individual curves shown in FIGS. 26 through 30 are dependent on the individual design parameters of a specific function generator. In order to vary the slope of the curve, or function, design parameters such as the size of the gap in both the uniformand non-uniform portions may be varied, or the number of turns per unit length associated with the coil may be varied, or both. The functional relationships illustrated in FIGS. 26 through 30 are all applicable to direct current, pulsed current, alternating current or a continuous wave operation.

Although we have discussed the relationships and results obtainable with concentric spaced apart anodes and cathodes, and magnetic fields applied thereto, the principles associated therewith and the results obtained therefrom are equally applicable to non-concentric arrangements as well, such as for example, wherethe anode is annular and in surrounding relation to the cathode but not coaxial therewith. Further, the principles of this invention are also applicable to planar components and/or fields, such as shown in FIGS. 3 and 4. For purposes of illustration, a shaped anode 102 is utilized. The shaped anode 102 is spaced from a plate-like cathode 108 so as to form a shaped gap 110 therebetween. The shaped anode 102 has a portion 104 which is inwardly tapered toward the cathode 108 and a portion 106 which is uniformly spaced from the cathode 108 and forms a minimum size gap. A magnetic field is applied to the gap 110 by means of a coil 112 through which the input current to the tube flows. The electric field within the gap 110 varies in the gap in the direction of the magnetic field, the direction being represented for illustrative purposes by flux lines 113. An electron tube constructed in this manner will function similarly to the previously described preferred embodiment having cylindrical components.

Modifications of the FIG. 3-4 embodiment analogous to FIG. 5, 6 and 8 embodiments 'will readily be apparent to the skilled art worker.

A further modification of the present invention is shown in FIG. 7. For purposes of illustration this modification is shown with reference to the embodiment shown in FIG. 1, although it would occur to one skilled in the art that such a modification may be accomplished with respect to the embodiment shown in FIG. 3 as well. The anode 44, cathode 42, and coil 48 are identical with those described with reference to FIG. 1 and have been given the same reference numerals. By providing another magnetic field to the gap 46 in addition to the magnetic field already present due to the coil 48, and combining these two fields, a switching function, or switching diode for the embodiment shown, may be obtained for the electron tube 40.

As shown in FIG. 7, a tubular permanent magnet 114 is disposed coaxial and concentric with the coil 48 in surrounding relation therewith. In order to provide the switching function, the permanent magnet 114 hassufficient field strength to hold the electron tube 40 at cut-off. The coil 48 which is disposed within the tubular permanent magnet 114, supplies a counter magneto-motive force of sufficient field strength to reduce the total gauss present between the cathode 42 and the anode 44 to a level permitting conduction to occur. The switching function results from the condition that when sufficient voltage or current is not supplied to the coil 48, which receives the input signal to the tube 40, the tube 40 is maintained in an off state, and is only placed in an on state when the current that is supplied to the coil 48 is sufi'lcient to produce an opposing magnetic field which overcomes the magneto-motive force of the field produced by the permanent magnet 114.

By shaping the various associated elements in a desired manner so as to alter the design parameters of the electron tube 40, the switching function can be combined with another function of the tube, such as those illustrated in FIGS. 26 through 30, so as to provide a dual or multi-purpose electron tube function generator. Ifdesired, this switching function can be accomplished without any structural modification to the embodiment shown in FIG. 1 by causing the current in the coil 48 to produce a magnetic field sufficient to cut-ofi the tube and prevent conduction. In this instance, a plate voltage which is sufficient to produce an electric field which overcomes the strength of the magnetic field and allows the tube to conduct is applied to the tube when conduction is desired, thereby providing the on-ofi' switching function.

Other modifications may be accomplished to the electron tube function generator of the present invention which will result in the tube performing multiple functions. Referring now to FIG. 22 which illustrates still another modification of the preferred embodiment shown in FIG. 1, the same reference numerals are used to identify corresponding parts. The anode 44 and the cathode 42 are each separated into two distinct portions, which are longitudinally spaced from each other. The anode 44 is separated into an upper portion 116 which contains the portion 70 uniformly spaced from cathode 42 at minimum distance, and the outwardly tapered portion 68, and a lower portion 118 which is cylindrical and uniformly spaced from the lower cathode portion 120 which is longitudinally separated from upper cathode portion 122. The anode 118 and cathode 120 lower portions preferably have inner and outer walls which are coextensive with therespective inner and outer walls of the anode 116 and cathode 122 upper portions. A schematic representation of the embodiment shown in FIG. 22 is illustrated in FIGS. 23 and 24. FIG. 23 shows a series connection for the coil48 with the anode of the tube; and FIG. 24 shows a parallel connection for the coil 48 with the anode. It will occur to one of skill in the art that by varying the parameters, such as the type of circuit connection of the coil with the anode of the tube, different functions may be obtained, such as described in greater detail hereinafter. The upper portions 116 and 122 of the cathode and anode respectively and the lower portions 118 and 120 of the cathode and anode constitute separate diodes that may be utilized to perform two separate functions for the electron tube function generator, as described in greater detail hereinafter.

Referring now to FIG. 25, a modification of the embodiment shown in FIG. 7 is illustrated, which FIG. 7 embodiment is modified in the same manner as the FIG. 1 embodiment was modified in FIG. 22. That is, the anode and cathode are divided to provide a dual purpose electron tube function generator having a switching function as one of its functions. In this instance, the permanent magnet 114 and the coil 48 extend in the direction of the longitudinal tube axis a sufficient distance so as to completely surround both the upper 116 and lower 118 portions of the anode 44. As in the previously described embodiment (FIG. 22) two separate diodes result from this arrangement and the tube is capable of providing multiple functions to be described in greater detail hereinafter, such as a constant current function and a switching function.

By applying the principles associated with the function generator of the present invention, as described with reference to the preferred embodiment and the modifications thereto, a considerable variety of circuit configurations having a multitude of purposes and results may be obtained. By way of illustration, several of these circuit configurations are illustrated in FIGS. 1 1 through 21 inclusive.

FIG. 1 1 illustrates a parallel circuit arrangement for the coil of the present invention, whose operation will now be described in greater detail.

This circuit arrangement may provide a constant current source having a function such as illustrated in FIG. 28, provided the gap or the magnetic field are properly shaped. In this arrangement, the current I,through the coil 48 combines with the current 1,, in the leg containing just the cathode and the anode of the tube to yield a total current I, which is constant within the control range. In FIGS. 32, and 11, 1, represents the current in the coil 48, I represents the current solely due to the electric field within the tube, and I, represents the total output current, which is the sum of the two currents I, and I,,. Referring now to FIG. 32, the total current I, rises as the sum of the two separate currents I, and I rise, as the input voltage V, applied to both coil and tube is increased from zero. When a voltage is reached which generates a magnetic field from the coil of sufficient strength to cut off a portion of the tube current, the tube current I,, will begin to drop as the coil current I, continues to rise, with further increases in voltage. The parameters of the tube and coil can be set so that from V, to V,,,, which is the control range of the function generator, the increase in coil current exactly matches the decrease in tube current, and the total current I, will remain constant. When V, is reached the tube current 1,, is zero, and the total current I, is now only the coil current 1,, which will then continue to increase with increasing voltage.

The parallel circuit arrangement can be used to provide rectification, clipping and shaping functions for the tube. FIG. 31 represents a graphical illustration of the rectification, clipping and shaping functions which may be obatined from the parallel circuit arrangement shown in FIGS. 11 and 12. For purposes of illustration the input to the tube is represented by a sine wave 145. If the tube is connected as a diode halfwave rectifier the output obtained from the tube will be a flattened wave 147 having a constant current portion 149 as opposed to the conventional half-wave sine wave 151. If the tube is connected in a conventional manner so as to provide fullwave rectification, the resulting wave which will appear may be represented by the curve 153 which consists of two flattened waves 155 and 157 having constant current portions 159 and 161. This output wave is flattened as was previously mentioned, as opposed to the normal diode full-wave curves 163 and 165. As will occur to one of skill in the art, other monotonic shapes than the constant current portion, may be achieved by proper design.

As can be seen in FIG. 12, the parallel circuit arrangement may be modified to include a variable resistor 121 in series with the coil 48 so as to adjust the current flowing through the coil 48 and thus the magnetic field resulting therefrom. A load 126 is connected in series with the parallel circuit arrangement of the coil 146 for obtaining an output from the circuit. If desired, although not shown, an impedance equality between both legs of this parallel circuit, or any other circuit in which the tube and its control coil are in parallel, may be achieved by inserting an inductance (with or without additional resistance), of a value equal to the inductance of the control coil, in series with the diode; and inserting a diode, with or without additional resistance, in series with the control coil, whose impedance matches that of the original diode.

FIG. 13 illustrates a series circuit arrangement for the coil 48 of the tube. In this arrangement the current through the coil and tube are always identical. FIG. 14 illustrates a parallel circuit arrangement for the coil 48 of the tube, similar to the arrangement shown in FIG. 12, with an additional coil 124 in series with the parallel arrangement so as to boost the flux density of the tube. In this arrangement the input current flows directly through the coil 124 so as to create an additional magnetic field in the direction of the field due to coil 48 and thus boost the total flux density of the tube. In this instance the series inductance 124 may be utilized to supply a bias magnetic flux, or minimum flux level, to the gap.

FIG. 15 illustrates a modification of FIG. 12 in that the parallel circuit has the load 126 included therein as opposed to being in series therewith, as in FIG. 12. This particular circuit (FIG. 15) is operable to protect the load 126 from excessive current surges in that as the input voltage is increased the current in the inductive leg containing the coil 48 is increased. The field produced by the coil 48 increases in intensity until at a predetermined value of current, the field produced places the tube in cut-ofi'. Thereby, an open circuit is presented across the load 126 and no current flows therethrough.

FIG. 16 illustrates an independent control circuit for the electron tube. The coil 48 has a separate power supply, V,, from the plate 44 which is supplied by a power source 64 and the control of the tube is, therefore, independent of the tube plate supply.

FIG. 17 illustrates a double parallel circuit arrangement wherein two diodes are operably connected together such as in the embodiment shown in FIG. 22. Three load positions are shown in the schematic and any one or all three positions may be utilized. In the event a load position is not utilized, the circuit should be completed thereacross by means of a connection. As can be seen by reference to FIG.'17, the current flowing through the leg containing one diode 121 controls the operation of the other diode 123 and vice versa.

FIG. 18 shows a circuit for a parallel connected switching tube, such as illustrated in FIG. 7, having an additional, external, control coil 128 to effect the operation of the tube.

FIG. 19 illustrates a circuit for a series connected tube having an additional external control coil 130 for effecting the operation of the tube wherein the current flowing through the coil 130 will determine the on or off state of the tube by affecting the flux density so as to remove the tube from cut-ofiif the tube is operated as an off-on switch. The direction of the field due to the coil 130 could be reversed if the operation of the tube were to be reversed. As was stated with respect to FIG. 18, FIG. 19 represents a tube such as shown in the embodiment of FIG. 7.

Several of the functions which may be generated by the electron tube function generator of the present invention may be combined to produce any of a wide variety of desired results. For example, as shown in FIGS. 20 and 21, the function generator of the present invention may be connected to provide a modulator trigger which will operate at very high power levels and at extremely high voltages. Utilizing the constant current functions which may be provided by the function generator of the present invention, a modulator trigger having a schematic as shown in FIG. 20 may be constructed. The external coil 177 is the modulator output triggering coil. A permanent magnet 179 is provided therewith. The modulator output triggering coil 177 is magnetically coupled to a current limiting function diode 181 having a series connected control coil 183v The total flux provided is the algebraic sum of the flux supplied by the permanent magnet 179, the triggering coil 177, and the current limiting coil 183. The change that occurs in the flux density in the gap of the current limiting function diode 181 between that which exists when the coil 177 is energized and that which exists when it is not, serves to switch the diode 181 on and off. In series with the current limiting function diode 181 and coil 183 is a constant current function generator 187, consisting of a diode 189 and its control coil 191. An overcurrent switching diode 185 is shown in FIG. 20 magnetically coupled to the constant current coil 191. The overcurrent switching diode 185 is switched off whenever an overcurrent appears in the constant current coil 19].

. FIG. 21 shows an alternative arrangement for the overcurrent switching diode 185, with the overcurrent diode being switched by the current limiting coil 183. This permits alternative designs which can provide for switching the overcurrent diode 185 either on or off when excessive currents appear in coil 183 because the total flux density influencing diode 185 can include that supplied from the permanent magnet 179, that from the triggering coil 177, and that from the current limiting coil 183. If desired, the modulator trigger 175 may be designed so as to consist of a constant current function diode electrically connected to a switching function diode, or the entire structure may be designed into a single electron tube package.

Several other applications of the function generator of the present invention and modifications thereto will occur to one of skill in the art, such as in circuits for filters, regulators, pulse flatteners, pulse shapers, protective devices, load compensators and magnetic amplifiers.

Although the present invention has been described with reference to varying the field strength in the gap in the direction of the longitudinal axis of the tube, the amount of magnetic flux in the gap may be varied instead, or in addition, in the direction of the transverse axis of the tube with similar results asa function generator.

The terms inner wall. and outer wall have been utilized throughout the specification with reference to the anode and cathode by way of example and not by way of limitation. Furthermore the anode outer wall although described as cylindrical need not be, and it would be obvious to one of skill in the art that these walls may be replaced by inner and outer surfaces of a thin sheet-like member wherein the inner and outer surfaces of the sheet substantially conform to the same shape.

It is to be understood that the above described embodiments of the present invention are merely illustrative of the principles thereof and that numerous other modifications and embodiments of the invention may be derived within the spirit and scope thereof.

What is claimed is:

l. A magnetically controlled electron tube function generator comprising:

a cathode disposed in the direction of the longitudinal axis of the tube,

an anode coextending with and spaced from said cathode so as to form a gap therebetween, said anode being at a different potential from said cathode so as to create an electric field therebetween; and means for obtaining an output as a desired function of the generator input, said means including means for providing an axial magnetic field to said gap normal to said electric field and means for varying in the longitudinal directionthe strength of one of the fields in said gap. 2. A magnetically controlled electron tube function generator comprising:

a cathode disposed in the direction of the longitudinal axis of the tube,

an annular anode extending in the direction of said longitudinal axis of the tube in surrounding relation with said cathode and spaced therefrom so as to form a gap therebetween, said anode being at a different potential from said cathode so as to create an electric field therebetween, and means for obtaining an output as a desired function of the generator input, said means including means for providing an axial magnetic field for said tube and means for varying the strength of one of the fields in said gap longitudinally in the direction of the longitudinal axis of said tube.

3. A function generator in accordance with claim 1 wherein said field strength varying means comprises means for varying said electric field strength in the direction of the longitudinal axis of the tube.

4. A function generator in accordance with claim 1 wherein said field strength varying means comprises said gap varying along at least a portion of the length of said cathode.

5. A function generator in accordance withclaim 4 wherein said anode has an innermost wall having a portion thereof non-uniformly spaced from said cathode, whereby to define said varying gap.

6. A function generator in accordance with claim 5 wherein said anode has an outermost wall uniformly spaced from said cathode along at least a portion of its length, said magnetic field providing means being disposed adjacent said outermost wall and coextensive therewith.

7. A function generator in accordance with claim 5 wherein said anode innermost wall has another portion which is uniformly spaced from said cathode along the length of said cathode, the spacing of said uniformly spaced portion determining the minimum anode potential for conduction.

8. A function generator in accordance with claim 5, wherein said anode innermost wall non-uniformly spaced portion is inwardly tapered toward said cathode.

9. A function generator in accordance with claim 5, wherein said cathode is outwardly tapered toward said anode innermost wall.

10. A function generator in accordance with claim 9, wherein said anode innermost wall non-uniformly spaced portion is inwardly tapered toward said cathode.

11. A function generator in accordance with claim I, wherein said magnetic field providing means is a coil, said magnetic field varying with said input signal.

12. A function generator in accordance with claim 1, wherein said field strength varying means comprises means for varying said magnetic field intensity in the direction of the longitudinal axis of the tube.

13. A function generator in accordance with claim 12, wherein said magnetic field providing means is a coil, the number of turns associated therewith varying in the direction of the longitudinal axis of said tube, said coil having said tube input applied thereto, said magnetic field varying withsaid input, said tube output being taken from said anode.

14. A function generator in accordance with claim 1, wherein said magnetic field providing means includes a first means for providing a magnetic field to said gap sufficient to prevent electrons from reaching said anode and causing conduction, and a second magnetic field providing means, independent of said first magnetic field providing means, for providing another magnetic field to said gap opposite to said first magnetic field, so as to be operable'to overcome the effect of said first magnetic field and cause conduction of electrons to said anode.

15. A function generator in accordance with claim 14 wherein:

said cathode is disposed along the longitudinal axis of the tube;

said anode is concentric with said cathode; and

said first and second magnetic field providing means are concentric and coaxial with said anode, said second magnetic field providing means being between said anode and said first means.

16. A function generator in accordance with claim 15, wherein said first means is a permanent magnet, and said second means is a coil having the input applied thereto.

17. A function generator in accordance with claim 1, wherein said anode and said cathode each include longitudinally spaced separate first and second portions extending in the direction of the longitudinal axis of said tube.

18. A function generator in accordance with claim 14, wherein said anode and said cathode each include longitudinally spaced separate first and second portions extending in the direction of the longitudinal axis of said tube.

19. A function generator in accordance with claim 18, wherein:

said field strength varying means comprises said gap varying along at least a portion of the tube axis between said anode and cathode first portions, and said gap between said anode and cathode second portions is uniform along said tube axis.

20. A function generator in accordance with claim 2, wherein:

said cathode is disposed along the longitudinal axis of the tube;

said anode is coaxial and concentric with said cathode;,and

said magnetic field providing means is disposed in surrounding relation with said anode and concentric therewith.

21. A magnetically controlled electron tube function generator comprising:

a cathode disposed in the direction of the longitudinal axis of the tube;

a magnetic field for said tube in the direction of the longitudinal axis of the tube and means for varying the amount of magnetic flux in said gap in the direction of at least one axis of the tube; and means for operating the tube so as to permit conduction between the cathode and anode throughout the duration of operation of the tube t t I I" l 

1. A magnetically controlled electron tube function generator comprising: a cathode disposed in the direction of the longitudinal axis of the tube, an anode coextending with and spaced from said cathode so as to form a gap therebetween, said anode being at a different potential from said cathode so as to create an electric field therebetween; and means for obtaining an output as a desired function of the generator input, said means including means for providing an axial magnetic field to said gap normal to said electric field and means for varying in the longitudinal direction the strength of one of the fields in said gap.
 2. A magnetically controlled electron tube function generator comprising: a cathode disposed in the direction of the longitudinal axis of the tube, an annular anode extending in the direction of said longitudinal axis of the tube in surrounding relation with said cathode and spaced therefrom so as to form a gap therebetween, saiD anode being at a different potential from said cathode so as to create an electric field therebetween, and means for obtaining an output as a desired function of the generator input, said means including means for providing an axial magnetic field for said tube and means for varying the strength of one of the fields in said gap longitudinally in the direction of the longitudinal axis of said tube.
 3. A function generator in accordance with claim 1 wherein said field strength varying means comprises means for varying said electric field strength in the direction of the longitudinal axis of the tube.
 4. A function generator in accordance with claim 1 wherein said field strength varying means comprises said gap varying along at least a portion of the length of said cathode.
 5. A function generator in accordance with claim 4 wherein said anode has an innermost wall having a portion thereof non-uniformly spaced from said cathode, whereby to define said varying gap.
 6. A function generator in accordance with claim 5 wherein said anode has an outermost wall uniformly spaced from said cathode along at least a portion of its length, said magnetic field providing means being disposed adjacent said outermost wall and coextensive therewith.
 7. A function generator in accordance with claim 5 wherein said anode innermost wall has another portion which is uniformly spaced from said cathode along the length of said cathode, the spacing of said uniformly spaced portion determining the minimum anode potential for conduction.
 8. A function generator in accordance with claim 5, wherein said anode innermost wall non-uniformly spaced portion is inwardly tapered toward said cathode.
 9. A function generator in accordance with claim 5, wherein said cathode is outwardly tapered toward said anode innermost wall.
 10. A function generator in accordance with claim 9, wherein said anode innermost wall non-uniformly spaced portion is inwardly tapered toward said cathode.
 11. A function generator in accordance with claim 1, wherein said magnetic field providing means is a coil, said magnetic field varying with said input signal.
 12. A function generator in accordance with claim 1, wherein said field strength varying means comprises means for varying said magnetic field intensity in the direction of the longitudinal axis of the tube.
 13. A function generator in accordance with claim 12, wherein said magnetic field providing means is a coil, the number of turns associated therewith varying in the direction of the longitudinal axis of said tube, said coil having said tube input applied thereto, said magnetic field varying with said input, said tube output being taken from said anode.
 14. A function generator in accordance with claim 1, wherein said magnetic field providing means includes a first means for providing a magnetic field to said gap sufficient to prevent electrons from reaching said anode and causing conduction, and a second magnetic field providing means, independent of said first magnetic field providing means, for providing another magnetic field to said gap opposite to said first magnetic field, so as to be operable to overcome the effect of said first magnetic field and cause conduction of electrons to said anode.
 15. A function generator in accordance with claim 14 wherein: said cathode is disposed along the longitudinal axis of the tube; said anode is concentric with said cathode; and said first and second magnetic field providing means are concentric and coaxial with said anode, said second magnetic field providing means being between said anode and said first means.
 16. A function generator in accordance with claim 15, wherein said first means is a permanent magnet, and said second means is a coil having the input applied thereto.
 17. A function generator in accordance with claim 1, wherein said anode and said cathode each include longitudinally spaced separate first and second portions extending in the direction of the longitudiNal axis of said tube.
 18. A function generator in accordance with claim 14, wherein said anode and said cathode each include longitudinally spaced separate first and second portions extending in the direction of the longitudinal axis of said tube.
 19. A function generator in accordance with claim 18, wherein: said field strength varying means comprises said gap varying along at least a portion of the tube axis between said anode and cathode first portions, and said gap between said anode and cathode second portions is uniform along said tube axis.
 20. A function generator in accordance with claim 2, wherein: said cathode is disposed along the longitudinal axis of the tube; said anode is coaxial and concentric with said cathode; and said magnetic field providing means is disposed in surrounding relation with said anode and concentric therewith.
 21. A magnetically controlled electron tube function generator comprising: a cathode disposed in the direction of the longitudinal axis of the tube; an anode extending in the direction of said longitudinal axis of the tube with said cathode and spaced therefrom so as to form a gap therebetween, said anode being at a different potential from said cathode so as to create an electric field therebetween; means for obtaining a tube output as a desired function of the tube input, said means including means for providing a magnetic field for said tube in the direction of the longitudinal axis of the tube and means for varying the amount of magnetic flux in said gap in the direction of at least one axis of the tube; and means for operating the tube so as to permit conduction between the cathode and anode throughout the duration of operation of the tube. 